There isn't a limit on how many you can upload. I see that you don't have very many points yet, so your scans will probably go to the queue until being approved by another member then added to the card after approval. Once you get more points, you can gain access to submit your scans without another member's approval. One thing the site is strict about though is that they are scans of the card and not photographs. Approved images usually show up within around 12-24 hours, though many will be quicker than this.
Matt Kenseth card collection is nearing 50% with over 2300 different cards. Always looking for the missing remainders to get to 100% completion.